I did badly for my O's, L1R4 21, English E8. Becuz I was busy
gaming way back then... So if I take on private diploma it will be
better right? as they don't see my O level result
It doesn't mean that if you have bad results, taking a private
cert will be better than a local poly diploma.
The 1st thing you should do is cut down on gaming and start to
really work hard. If you keep on gaming, no matter where you go,
your results will still be like crap. ( No Offence )
For example, there are people who get their ACCA cert in 2
years, and there are people who couldn't get it even after 6 years,
so go figure about it yourself.
Just as gunner suggested, retaking "O" level is an option, but
that is only if you are willing to put in extra effort and
time.
Another two questions in mind are what career do you want to
have next time in the future., and what courses interest you.
If you just try to jump into any course which will take you,
odds are your results will still be crappy as you do not have an
interest in these courses and will not be motivated to work extra
hard on your studies.